[Bug modula2/121629] Where to install 3rd party library .def files

[gaius at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121629
Bug 121629 depends on bug 121709, which changed state.

Bug 121709 Summary: [16 regression] Failed bootstrap in m2 (m2/gm2-lang.cc:547:39: error: ‘PREFIX_INCLUDE_DIR’ was not declared in this scope)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121709

           What    |Removed                     |Added
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             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED